hey guys i dont rly understand how to set up a PA system w/ a whole band, i dont rly need to set up one right now but just for future reference... also how do bands who play in stadiums play through an entire wall of amps with only a single head and if they dont do that how do they get themselves heard in a stadium. Thx
mic up the amp to the stadiums sound system. you only need enough "stacks" on stage to hear yourself, the rest will be mic'd.
well a PA system consists for a few things

mixer- you plug your microphones, and an other sound related stuff into this. Then you can control the levels of everything you put into it

power amp- the sound from the mixer travels into the power amp which makes the signal very big and loud

speakers- these are pointed towards the audience so they can hear whatever you have mic'ed up.

monitors- these speakers are pointed towards the actual preforms so they can hear what they are doing, this helps the singer sing in key, and everyone play in tempo. So bands have in ear monitors, same concept but the speakers are in their ears.

when you step up a pa system, such as when you play in a stadium haha. You mic every instrument; the guitar cabs, the singer, bass amp, every drum in the drum set. The sound goes into a mixer where a team of people make the levels perfect as sound is coming out of the speakers and monitors.

ask questions if you have any, i'll be glad to answer
you would need a mic for each different sound source. A mic in front of the guitar amps, bass amps, one for each person singing, and a minimum of two for the drums (one on the kick and one overhead). Take all these mics and run them into the 'house mixer' board, which will be already hooked up to the sound system. If there is no 'house mixer' then your show probably isn't too big and will be fine PA-less.

Idk how/if bands only use one head for their huge assembly of stackage at stadium gigs, but they are definitely mic'ed into the PA system.
thanks that helped alot.... i dont rly play gigs but it was a rly burning question... ok so to clarify the all the mikes are hooked up to 1 sound board and that sound board is hooked up to speakerss (the PA system) then you have seperate monitors? im still confused about the monitors and how they r hooked up